This invention relates to a clearance seal construction for a pump. More particularly, this invention relates to a clearance seal construction disposed adjacent a pump shaft bearing frame for preventing lubricating fluid from migrating away from the bearing frame.
Environmentally hazardous fluid such as acids, oils, and toxins which can cause serious harm to the environment often need to be pumped through fluid flow systems from one location to another. When pumping such dangerous flow materials, it is important that neither the liquid nor the gases which are often released by the liquid escape to the atmosphere or pump areas outside the desired fluid pumping path.
Environmentally safe pumps used in such situations typically include a motor for driving a pump shaft, the pump shaft being affixed at one end to a fluid pumping impeller assembly and at the other end to the motor output shaft. Conventional single and double row bearings (e.g. ball bearings) are typically disposed within a lubrication chamber adjacent the motor for rotatingly supporting the pump shaft and/or motor shaft. Such lubrication chambers generally circumferentially surround the pump shaft and define a lower well portion to be filled with lubricating oil or other conventional lubricating liquid.
Co-axially spaced bearing frames housing the aforesaid bearings are typically disposed within the lubrication chamber, one on either side thereof, as known in the art. These bearings provide for substantially frictionless rotation of the pump shaft while simultaneously supporting it against vibration. The purpose of the lubricating oil within the chamber is to lubricate the co-axially spaced bearings housed within their corresponding bearing frames. Such lubrication is desired in order to reduce the friction associated with rotation of the pump shaft and prolong the life of the pump's moving parts.
It is known to dispose seals adjacent such bearing frames so as to prevent lubricating fluid migration away from the bearings. See U.S. Pat. Nos. 4,420,515, 4,429,883, 4,840,385, 5,158,304, and 5,174,583 just to name a few. The end result of such a migration/leakage could be a contaminated environment, excess fluid buildups in other parts of the pump, or contamination of the fluid being pumped. Additionally, if the lubricating fluid leaks out of the lubrication chamber, the bearings disposed therein are left without a means for lubrication thus leading to increased maintenance requirements and reduced operating life of the pump.
It is also known to provide a pump with a rotating clearance seal spaced axially along the pump shaft from the bearing frame. Typically, a bearing lock nut is disposed axially along the pump shaft between the bearing frame and the rotating seal. Such seals often include a rotating member affixed to the pump shaft and a stationary member circumferentially surrounding the radially exterior periphery of the rotating member, the rotating member having a plurality of labyrinth-type grooves defined therein for creating a sealing air flow between the members which prevents lubricating oil from migrating away from the bearing frame during rotation of the pump shaft and attached rotating member.
One drawback associated with the aforesaid clearance labyrinth-like seal construction is the amount of space it takes up axially along the pump shaft. Pumps often must be positioned in tight-fit places. So, the more compact the pump, the better. The aforesaid disposition of the bearing lock nut along the pump shaft axially between the bearing frame and the seal unfortunately increases the overall axial length of the pump. Also, the further away from the bearing frame the seal is disposed, the greater the volume of space therebetween for lubricating fluid to collect after it leaks through the bearing frame. This creates a problem because the amount of pressure put on the seal is a function of the amount/volume of fluid disposed adjacent thereto. In other words, the more fluid present in a chamber adjacent the seal, the harder it is for the seal to properly function.
Before discussing another drawback associated with such prior art labyrinth-type clearance seals, it is necessary to recognize that a problem also exists with respect to foreign materials entering the lubrication chamber by way of the bearing frame. Contaminants present exterior the lubrication chamber often make their way thereinto in the prior art. This leads to increased friction within the lubrication chamber and causes the moving parts therein (e.g. bearings) to wear out faster than otherwise. Additionally, such leakage into the lubrication chamber (and bearing frame) leads to quicker breakdown of the lubricating fluid and increased friction associated with rotation of the pump shaft. Accordingly, it is highly desirable to prevent foreign materials from leaking into the lubrication chamber and adjacent bearing frames.
The aforesaid prior art labyrinth-type clearance seals spaced axially from adjacent bearing frames are sometimes not strong enough to simultaneously or otherwise prevent both (i) lubricating fluid from migrating away from the bearing frames; and (ii) contaminants or foreign material from reaching the lubrication chamber or adjacent bearing frames.
It is apparent from the above that there exists a need in the art for a pump shaft seal construction having relatively few moving parts and a simple construction requiring little maintenance. Such a seal should also be compact in nature and strong enough to simultaneously both (i) prevent lubricating fluid from migrating away from an adjacent pump shaft bearing frame; and (ii) deter contaminants or other foreign materials from reaching the bearing frame.
It is the purpose of this invention to fulfill the above-described needs in the art, as well as other needs apparent to the skilled artisan from the following detailed description of this invention.